The July 8 event in Washington D.C. was also participated in by House Speaker John Boehner and Senate Majority Leader Mitch McConnell.

The Vietnam War taught Americans many lessons, "many hard-won, some difficult to swallow," Carter said.

He noted the Defense Department has more than 650 employees devoted to accounting for those missing-in-action from US wars, including the 1,627 service members still missing from Viet Nam.

Former Defense Secretary Chuck Hagel, himself a Viet Nam veteran, told the crowd that "there is no glory in war, only suffering".

He also described the night his personnel carrier was ambushed, leaving his brother and others wounded. As they waited for medical evacuation by helicopter, Hagel swore to himself that he would work to make war a last resort for resolving disputes between countries.

Regarding the historic meeting between General Secretary of the Communist Party of Viet Nam Nguyen Phu Trong and US President Barack Obama at the White House on July 7, Hagel said the talks were not meant to recall the past but work towards the future, adding that the US learned many lessons from the Viet Nam War, and will work to avoid repeating them in the future. — VNS